From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=0.2 required=5.0 tests=BAYES_00,INVALID_MSGID,
	REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,b8effe21a2a8e1cb
X-Google-Attributes: gid103376,public
From: Al Christians <achrist@easystreet.com>
Subject: Re: An interesting object lesson (Ada vs C)
Date: 1998/04/26
Message-ID: <354428B4.674A@easystreet.com>#1/1
X-Deja-AN: 348003073
Content-Transfer-Encoding: 7bit
References: <dewar.893600073@merv> <6hvpf2$77d$1@news.hal-pc.org>
Mime-Version: 1.0
Reply-To: achrist@easystreet.com
Content-Type: text/plain; charset=us-ascii
Organization: Trillium Resources Corporation
Newsgroups: comp.lang.ada
Date: 1998-04-26T00:00:00+00:00
List-Id: <comp.lang.ada>


Jonathan Guthrie wrote:
> 
> 
> Elapsed time to my solution of the problem: 45 seconds.  Eliminate the
> warnings, and the code gives (on my computer)
> arctan 0.5 = 0.463648
> Clock ticks:  1933
> 
> > arctan 0 = 3.25435e-229
> > Clock ticks:  2160
> 
> Wow!  I've got a faster computer!  (I didn't know that was possible!
> Maybe it isn't possible.  What value of CLOCKS_PER_SEC does he
> have?  Mine is 100.)
> 
> > How did x get set to 0!?!?!?!?
> 
> It didn't.  It got DISPLAYED as 0.  That's what happens when you use
> compiler-specific extensions (as "long double" is, at least for the
> time being) without understanding the underlying mechanisms.  By the
> mechanism that printf uses to accept parameters, it had every reason to
> expect that you would pass it a double, but you passed it a long
> double.
> 

If x didn't get changed,  howcome the answers for arctan are so
different?
I put the code posted into MS VC++ v5 with the strictest warning level,
and
I got the 0.463648 answer (looks reasonable for arctan 0.5) with no
warnings
at all.  MingW32, based on GCC gives the warnings and the arctan 0
answer.

I guess that MS would probably say that you don't need to issue the
warning
if you don't drop the ball.  

This obviously has profound implications for Ada, but I won't mention
them
here for lack of interest in compiler/vendor/ .../ .../language  wars.  


Al